Technical Field
The present disclosure relates to an engine that can be widely used in fields of motor vehicle and power machinery. In particular, the present disclosure relates to a rotary engine that performs power strokes through the rotary motion of a rotor, and a rotary unit thereof.
Background Art
In a conventional engine, a working piston performs a reciprocating rectilinear motion in a cylinder, and the rectilinear motion of the piston is converted into rotary motion by using a crank link mechanism. In such a conventional engine, four-stroke engine has a complicated valve mechanism, a small power-weight ratio and a low power per liter; comparatively speaking, although two-stroke engine has a simple structure and a high power per liter, it is very difficult to achieve good lubrication due to excessively large fuel consumption and environmental pollution as well as its own structure, causing its use range narrow.
In contrast, it has been suggested that an engine having a rotary piston mechanism can be used. For example, CN101403335A discloses an engine including a dual rotary piston mechanism. However, this engine is disadvantageous in terms of a small power-weight ratio, reciprocating motion existing in the valve mechanism, and eccentric rotation being prone to generate vibration, etc.
Different from the conventional reciprocating engine, a rotary engine directly converts the combustion expansion force of the combustible gas into driving torque, and thus the unnecessary rectilinear motion is cancelled. For example, the existing triangle rotary engine performs power stroke once every revolution of a spindle, and thus is advantageous in terms of a higher power per liter as compared to the general four-stroke engine which performs power stroke once every two revolutions of the spindle; moreover, the rotary engine can reach a higher operating speed without a precise crankshaft balancing due to its operating characteristics; additionally, the whole rotary engine only has two rotating parts, and thus has a considerably simplified structure with greatly reduced possibility of failure, as compared to the general four-stroke engine which has more than twenty moving parts such as intake valve, exhaust valve, or the like. In addition to the above advantages, the rotary engine is also advantageous in terms of a smaller volume, a light weight, a low center of gravity and a high power, etc.
In spite of that, the existing rotary engine still has the following drawbacks:
Firstly, although the rotary engine eliminates the impact occurred during the reciprocating motion of the piston, additional eccentric vibration is generated during operation of a rotor due to the eccentric structure thereof. In order to eliminate the eccentric vibration, a balance weight is required to be added which is vibrated in a direction opposite to the vibration direction of the rotor to reduce this vibration. Meanwhile, during the power stroke of the rotary engine, a local area of a cylinder block always suffers a huge impact, which causes a severe localized wear of the engine body, resulting in a non-uniform wear of the engine, thereby significantly reducing the lifespan of the engine.
Secondly, the rotor directly contacts with and drives the spindle to rotate the rotary engine while the rotor itself rotates eccentrically within the cylinder, behaving as a big gear fitted over an outer periphery of the spindle and moving eccentrically. The spindle journal is relatively small, causing a driving manner in which the big gear drives a small one such that the torque thereof is greatly reduced, which is also a main reason why the rotary engine is not widely available yet.
Thirdly, the rotary engine consumes a larger amount of fuel. It is mainly because the shape of the engine combustion chamber is adverse to complete combustion and the flame propagation path is longer, such that the fuel consumption and engine oil consumption are increased correspondingly. Moreover, the rotary engine has a low compression ratio due to its own structure, can only employ spark ignition but not compression ignition, and thus diesel oil can not be used.
In addition, since the adjacent cavities in the triangle rotary engine are sealed by a radial blade, the radial blade and the cylinder block undergo a trochoidal motion at an extremely high linear velocity during operation, which easily causes the radial blade worn quickly and generates tremulous ripples in the cylinder block, resulting in problems such as defective tightness, gas leak, or the like after the engine is used for a period of time, which in turn considerably increases the fuel consumption and pollution, thereby having an effect on the lifespan of the rotary engine as well.
To this end, although the existing rotary engine has many advantages as compared to the conventional rectilinear reciprocating engine, since the rotary engine has the above drawbacks, it is hard to use and popularize.